Guide to mains grid connect solar power

Note from Michael: this is the second article in my series on solar power; the original article which contains links to this guide and other aspects of solar power equipment can be viewed here.

This article was first published in June 2008, last updated in December 2011.

Often when we think of a solar power system, we envision a hugely complicated setup and lots and lots of batteries. That’s not necessarily the case in a mains grid connect system.

Grid connect solar power is usually the most suitable and economical choice for premises with an existing mains supply; particularly if you’re lucky enough to have renewable energy rebates in your country and many do -including the USA, UK, Canada and Australia.

A grid connect system consists of just 4 main elements:

solar panels
– panel mounting system
– suitable wiring
– a grid connect inverter

How does grid connect work?

The beauty of a grid connect solar power system is its simplicity:

  • The solar panels when exposed to sunlight generate DC electricity
  • The DC charge goes through a special grid connect inverter that converts it to a voltage suitable for use by household appliances in whatever country you are in.
  • Any excess electricity is then fed back into the mains grid. Your meter will spin backwards!

Grid connect solar system
(Image courtesy Energy Matters Australia – grid connect solar specialists)

What happens at night time and on cloudy days?

Solar panels will still generate a little electricity on cloudy days, but the amount is far less than what the panel is rated and of course, at night, they’ll generate nothing at all. On a grid connect system, as you’ll still have access to mains power; so whenever the system isn’t generating enough to meet your needs, it will draw the extra required from the grid – this is seamless, there’s no switches to flick.

How about during a blackout?

During a blackout, you’ll be just like everyone else – without power. The inverter will shut down to avoid damage to appliances in your home and to prevent electricity back feeding into a grid. To get around the loss of power, you can have a battery backup, but this will add a fair bit extra to the cost and really isn’t necessary if your existing power supply is pretty reliable.

Is there much maintenance?

Very little, occasionally brushing any dust or grime from the panels will help with performance and in most cases if your roof and/or the panels suitably angled, the rain will keep them clean.

Can you set up a grid connect solar system yourself?

No, in most countries you’ll be required to have a suitably qualified solar installer to do the work for a couple of reasons:

a) There are high voltages involved which could present a risk to you if you do it yourself and an ongoing risk to others if not installed properly.

b) You’ll only get a rebate if the installation has been performed by an approved provider.

Location, location, location

In order to get the most bang for your buck from a grid connect system, in the southern hemisphere you’ll need a north facing roof with adequate shade-free space. In the northern hemisphere, the roof where the panels will go need to be facing south. In both scenarios, it’s good to have a decent angle on your roof for the purposes of keeping the panels clean and squeezing the most from the sunlight, but this can be gotten around using angle mounts.

Show me the money – how much?

This greatly depends on the type of system you install – you don’t need to install one that entirely services your needs. You can start out with a small unit and then build on that.

Depending on the country, there will be a minimum configuration needed in order to get a decent renewable energy rebate. In Australia, the rebates are currently up to around $3,000; depending on the size of the system and where you live. For example, a 1.5 kW system in South Australia will cost you around AUD $3,000 after the rebate. While the current rebates aren’t as generous as the previous system; the new scheme is not means-tested.

For a grid connect system that will fully service your home without any modifications to your electricity usage, you’ll be looking at around $14,000 – $20,000 fully installed before any rebates, but as I mentioned in my article on solar power basics, there’s ways to get this cost right down aside from any renewable energy rebates that may be available.

Surplus solar electricity – the bonus

On any given day, there’s what’s called “peak” sun hours and during these hours a grid connect system could churn out more electricity than what can be used by the household; so it’s simply fed back into the grid. But this doesn’t mean you’re giving your utility the juice for free!

On top of any renewable energy rebate you may be entitled to, if you produce more electricity than what you use, you’ll most likely be credited for that on your bill and those credits will come off the total bill, usually at the same price that they sell the electricity to you.

Some countries are especially generous and have established feed-in tariffs which guarantee the amount a householder will get for their excess production. Probably the most successful scheme has been in Germany where people with grid connect systems get a guaranteed payment of an incredible four times the market rate.

It’s this feed in tariff (FIT) that has made Germany one of the superstars when it comes to solar power – the tariffs won’t last forever, but they’ve been available for many years and have had a four-fold effect:

a) encouraging the uptake of solar power
b) encouraging people to use less electricity in order to maximize their return from the feed in tariff.
c) The soaring popularity of solar power in Germany has also helped push down the price of related equipment
d) Germany now has a huge home-grown solar equipment production industry, plus many new jobs have been created in related services.

Those Germans are pretty cluey folk – I hope that many other governments, including our own wake up and follow their lead if they are truly serious about dealing with global warming. I mean, Germany’s not really known for sunshine is it? Imagine what could be achieved in countries such as Australia and the USA with a real commitment to grid connect solar energy! Bug your local government representative about it.

A mains grid connected solar power system may not the cheapest thing around, but you may be pleasantly surprised by rebates and feed in tariffs that are available, making your dream of of being directly powered by renewable energy a reality!